Cured release coating layer-forming organopolysiloxane compositions, by forming a cured release coating when cured on the surface of a substrate, e.g., various types of paper, synthetic films, fibers, textiles, and so forth, are able to impart thereto nonadhesiveness, i.e., releasability, versus tacky substances and for this reason are widely used in the production of pressure-sensitive adhesive tapes and various types of labels.
These cured release coating layer-forming organopolysiloxane compositions must exhibit, inter alia, the following properties: the cured coating layer formed by the cure of the composition must not have a negative influence on the pressure-sensitive adhesive layer, i.e., the components of the coating must not migrate to the pressure-sensitive adhesive layer (this is evaluated via, for example, the residual adhesiveness of the pressure-sensitive adhesive layer), and the cured coating must exhibit releasability. The releasability exhibited by the cured coating is a particularly important requirement with regard to the specifications of pressure-sensitive adhesive tapes and labels, and different release force levels must be provided as a function of the particular application. In addition, the thusly modified release force must also be stable and must not undergo timewise variations. The temporal stability of the release force is a particularly important problem when a medium to heavy release force is required.
Within the sphere of technology for adjusting the release force of the cured coating, methods have been disclosed for obtaining a heavier release by adding a tacky polyorganosiloxane resin component to an addition reaction-curable organopolysiloxane composition that itself provides a light release force (refer to Patent References 1 to 6). The addition, for example, of hydroxyl-containing polydimethylsiloxane has also been proposed as method of providing a lighter release (Patent Reference 7).
Similarly, in the field of silicone pressure-sensitive adhesives that form a silicone adhesive layer on a substrate by an addition reaction cure, art is already known in which the condensation product of a hydroxyl-functional polyorganosiloxane resin component with a hydroxyl-functional polydimethylsiloxane is used to raise the tackiness (Patent References 8 and 9).
Art is likewise already known in which the condensation product of a hydroxyl-functional polyorganosiloxane resin component with a hydroxyl-functional polydimethylsiloxane is incorporated into a textile printing glue or a cured release coating-forming organopolysiloxane composition, and it is also known that the resulting compositions exhibit appropriate releasabilities (Patent References 10 and 11).
The art is also known of incorporating, as a heavy release control agent, the partial condensation product of an alkenyl-functional organopolysiloxane with a hydroxyl-functional polyorganosiloxane resin component that contains the tetrafunctional or trifunctional unit (Patent Reference 12) or the condensation product of an organohydrogenpolysiloxane with a hydroxyl-functional polyorganosiloxane resin component that contains the tetrafunctional unit (Patent Reference 13).
However, the coatings yielded by the compositions cited above have not exhibited a satisfactory temporal stability by the modified release force, and as a result the release force lightens with the passage of time. In addition, with regard to the art of incorporating a known condensation product of a hydroxyl-functional polyorganosiloxane resin component with a hydroxyl-functional polydimethylsiloxane in order to generate a heavy release behavior, the release modifier-containing composition is prone to exhibit an increased viscosity. Another problem here has been migration of coating components into the pressure-sensitive adhesive layer, causing a rise in the residual adhesiveness of the pressure-sensitive adhesive layer. Moreover, during release of the pressure-sensitive adhesive, release from the pressure-sensitive adhesive surface may not proceed smoothly when the release velocity is increased. Microadjustment of the release force is quite difficult with these release modifiers and cured release products, and there has been desire from a practical standpoint for a release modifier that would provide the ability to microadjust the release force. Furthermore, the alkenyl-functional MQ resin used as a starting material is also relatively expensive, and this has created desire for a release modifier that can be provided less expensively in mass quantities.    [Patent Reference 1] JP 52-086985 A    [Patent Reference 2] JP 59-084935 A    [Patent Reference 3] JP 01-215857 A    [Patent Reference 4] JP 03-002270 A    [Patent Reference 5] JP 04-226120 A    [Patent Reference 6] JP 11-106703 A    [Patent Reference 7] JP 08-217980 A    [Patent Reference 8] JP 02-269157 A    [Patent Reference 9] JP 10-110156 A    [Patent Reference 10] JP 57-029676 A    [Patent Reference 11] JP 2008-013613 A    [Patent Reference 12] JP 2007-106908 A    [Patent Reference 13] JP 63-017290 A